Rising fuel prices are reawakening interest in turbocharging, an old engine technology that can improve fuel economy and boost power.
Automakers are offering more turbocharged gasoline-power cars and have plans for others. At the same time, diesel-power cars and trucks  always turbocharged  are becoming more common.

Turbocharging can cut fuel consumption 10% to 20% in gasoline-power vehicles. It uses smaller engines and boosts power  and thus fuel consumption  only when needed. Diesels get about 30% better fuel economy than similarly powerful gas engines.

Turbocharging is widely used where fuel prices are higher.

"We're beginning to see increased interest from U.S. automakers as they look to gas turbos to attract younger, affluent, performance-oriented buyers," says Martin Verschoor, vice president of technology for Honeywell Turbo Technologies. "But the real change will be the likely adoption of turbo diesels in the U.S. Who doesn't want a high-performance car or truck that can get over 45 mpg?"

The first quarter this year, 42 car and truck models were available with turbocharged engines  16.3% of the 258 models available, according to the Power Information Network, an affiliate of J.D. Power and Associates. That's up from 28 turbo models first quarter 2002, or 11.3% of 248 models.

R.L. Polk data show that 317,603 turbocharged cars were newly registered last year, 4.1% of all new cars. That's down slightly from 4.2% in 2002, but well above 3.2% in '00. In Europe, with doubled fuel costs, 43% of cars are turbocharged.

Roadblocks

Two question marks make it unclear whether the surge in activity, especially among automakers, is the beginning of a trend or a blip en route to other technologies.

 Automakers are wrestling with whether to step up turbo development and production at the expense of, say, advances in gas-electric hybrids and other technology that can improve both performance and fuel economy.

Torque is low-speed power that lets a vehicle shoot from a stoplight or tow a heavy load. It mainly depends on how big an engine's displacement is. "You want to feel that torque," says Robert Larsen, director of the Center for Transportation Research at the Energy Department's Argonne National Laboratory. "That's what Americans are used to, and that tends to be the disadvantage of these smaller-displacement engines."

"Our customers tend to put some stock in displacement and number of cylinders," even when a smaller, turbocharged engine performs better, says Dan Kapp, Ford Motor's chief powertrain engineer.

Other than its Volvo brand, Ford sells no turbocharged cars in the USA. "We're not against it. We're looking at it, along with many other technologies," Kapp says.

One reason not to build a few to test the market: "From a cost perspective, it is not insignificant. ... It's a $300 to $500 addition" per car, he says  in an industry where a part that adds $1 is iffy.

Nonetheless, Larsen notes, everybody is working on advanced technology engines that would require a feature such as turbocharging for proper operation.

In the works

While a huge boost in the number of U.S.-market turbo gas engines can't happen overnight, automakers and turbo suppliers have serious development underway, drawing on experience from producing millions of turbo engines annually for other markets.

"We know that turbocharged engines are more efficient at the same power level, and we do have some experimental (turbocharged) vehicles that do feel like driving a large-displacement engine," says Ko-Jen Wu, manager of advanced technological development at General Motors' engine and transmission operations.

GM has a rich tradition of producing turbo engines, he says. Its newest line of engines, so-called Ecotec four-cylinders, were designed to be compatible with turbochargers.

For years, turbochargers have routinely been used on heavy- and light-duty diesels and on aircraft engines. But gasoline engines' higher exhaust temperatures and wider range of engine speeds make turbocharging them a challenge.

The technically enticing part is that turbos are driven not by a power-robbing accessory belt on the engine, but rather by the engine's otherwise wasted exhaust gas. The drawback has been a pause, called turbo lag, between when the driver steps on the gas and when the engine's exhaust begins to spin the turbine wheel fast enough to provide a significant power boost.

Most modern turbochargers use smaller, lighter parts to cut inertia and minimize lag.

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